Complete the series: a, c, e, g, ?

B. H

What letter should replace the question mark in the series: z, x, v, t, ?

A. R

Which letter should replace the question mark in the series: B, D, F, H, ?

D. I

Find the odd one out in the series: A, D, G, J, K, N

A. K

What letter should replace the question mark in the series: z, x, v, t, ?

C. Q